Selected Abstracts

JOURNAL OF FOOD BIOCHEMISTRY, Issue 3 2004CARMEL C. WILLSRainbow trout were killed by two methods, asphyxiation and clubbing.
The concentration of ATP in specimens of skeletal muscle taken immediately after death was significantly (P<0.01) higher in clubbed (4.41 ± 0.86 ,mol/g) than in asphyxiated (2.00 ± 0.69 ,mol/g) fish.
The shear force (Warner-Bratzler) required to cut the muscle was higher (P<0.05) in clubbed (8.33 ± 0.61 N) than in asphyxiated (6.85 ± 0.98 N) fish.
Changes in the concentration of adenine nucleotides and in shear force were measured at intervals during storage at 3C and - 30C.
The K value was calculated and was found to be correlated inversely with changes in shear force, Torrymeter readings and sensory assessment.
There were no significant differences in the concentrations of ATP and metabolites between muscle sites.
There were no differences in shear force measurements between the locations sampled nor between muscle taken from the right and left sides of the fish.
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JOURNAL OF FOOD SCIENCE, Issue 9 2007Y.-C. Chen
ABSTRACT:, Protein, lipid, and insolubles (bones, skin, scales, fins, insoluble protein, and more) were recovered from rainbow trout processing by-products by means of isoelectric solubilization/precipitation at basic pH and acidic pH. Isoelectric solubilization/precipitation of the trout processing by-products resulted in the recovery of protein that was higher (P < 0.05) in essential amino acids (EAAs), non-EAAs, and total EAA/total AA ratio when compared to the processing by-products.
Basic pH treatments yielded a higher (P < 0.05) content of EAAs than the acidic pH treatments.
Nutritional quality of the recovered protein was high based on EAAs meeting the FAO/WHO/UNU recommendations for adults.
The presence of omega-3 and omega-6 fatty acids (,-3, ,-6 FAs) and the ,-3/,-6 ratio in the recovered lipids were similar to the trout processing by-products, indicating that the pH treatments had no effect on these FAs.
Ca and P contents of the processing by-products exceeded the recommended dietary allowances (RDA), but Fe and Mg did not.
Basic pH treatments yielded protein with the lowest (P < 0.05) amount of minerals and the highest (P < 0.05) amount of Ca, P, and Mg in the insolubles when compared to acidic pH.
The isoelectric solubilization/precipitation of the processing by-products effectively removed minerals from the recovered protein without removal of the bones, skin, scales, fins, and so on, prior to processing.
The results indicated that isoelectric solubilization/precipitation, particularly at basic pH, permitted recovery of high-quality protein and lipids from fish processing by-products for human food uses; also, the recovered insolubles may be used in animal feeds as a source of minerals.
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JOURNAL OF FOOD SCIENCE, Issue 7 2006Y.C. Chen
ABSTRACT:, A commercial diet for rainbow trout (Oncorhynchus mykiss) was supplemented with 0 (control), 8.5%, or 15.0% (w/w) of flaxseed oil (FO).
Trouts were harvested on days 0, 30, 60, 90, and 120.
Boneless skinless trout fillets were recovered from fish and analyzed for fatty acid profile (FAP) and total fat.
While the total fat levels of fillets were not (P > 0.05) affected by FO supplementation, the FAP was.
The lowest (P < 0.05) proportion of saturated fatty acids was obtained from 15%, followed by 8.5% FO group, and the control group.
The opposite results were observed for the unsaturated fatty acids.
The highest (P < 0.05) content of omega-3 fatty acids (,-3 FA) in fillets was determined in the 15.0%, followed by the 8.5% FO group, and the control group.
While the 15.0% and 8.5% of FO supplementation increased (P < 0.05) concentration of linolenic acid (ALA, 18:3n3) in fillets, the eicosapentaenoic (EPA, 20:5n3) and docosahexaenoic acids (DHA, 22:6n3) contents decreased (P < 0.05).
At the same time, higher (P < 0.05) concentration of linoleic (L, 18:2n6) and lower (P < 0.05) concentration of arachidonic acids (AN, 20:4n6) in fillets were obtained in the 15.0% FO group compared with the control group.
The ,-3/,-6 FA ratio was also improved (P < 0.05) by supplementing basal diet with 15.0% FO.
Our results suggest that trout fillets with enhanced content of ,-3 FA can be developed from trout raised in aquaculture systems fed diets supplemented with 15.0% FO.
These fillets could be a basis to develop novel functional aquatic foods for some niche markets.
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Leptin mRNA and Protein Immunoreactivity in Adipose Tissue and Liver of Rainbow Trout (Oncorhynchus mykiss) and Immunohistochemical Localization in Liver

ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 6 2009B. Pfundt
Summary
Leptin is an important modulator of energy balance and metabolism in mammals, but for evolutionary older vertebrates like fish, the first reports on leptin expression were only recently characterized and the functional role scarcely.
In this study, we demonstrated leptin immunoreactivity in liver tissue of rainbow trout (Oncorhynchus mykiss) by immunohistochemistry using three different polyclonal antibodies against mammalian leptin.
Immunoreactivity was observed in hepatocytes and also in parts of the biliary system.
Using Western blot, we detected an immunoreactive band of about 16 kDa in serum and visceral adipose tissue (AT) of rainbow trout.
The presence of leptin in fish AT has been doubted in other studies.
Besides the immunoreactivity, leptin mRNA was detected in trout AT albeit not in all animals sampled.
Our observations add further evidence to the concept of AT being a source of leptin in trouts.
Moreover, the cellular localization of leptin immunoreactivity in liver opens up new vistas for understanding the functional role of leptin in teleosts.
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Quantifying risks of volitional consumption of New Zealand Mudsnails by Steelhead and Rainbow Trout

AQUACULTURE RESEARCH, Issue 4 2010Rolita Louise Bruce
Abstract
To assess the risk of transferring alien, invasive New Zealand mudsnails (NZMS) Potamopyrgus antipodarum with shipments of live rainbow or steelhead trout Oncorhynchus mykiss, we conducted laboratory trials to quantify and determine the volitional ingestion of snails from the bottom of laboratory tanks.
Approximately, 2000 snails were placed on the bottom of a test tank and groups of 10 fish were added to each tank.
After 48 h, the fish were removed, euthanized and the snails in the gastrointestinal tract were counted, and the proportion of snails remaining in each tank was measured.
We found that both rainbow trout and steelhead consumed NZMS, but rainbow trout consumed nearly twice the number of snails that were consumed by steelhead trout.
Feeding fish a maintenance diet increased the total consumption of snails by fish to an average of 64.5 snails per rainbow trout.
Our study suggests that management strategies that depurate fish without feed for 48 h to reduce the risk of transfer of NZMS are not viable in preventing the transport of snails if rearing waters contain snails.
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ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2006Birgit Hoger
Abstract
Rainbow trout (Oncorhynchus mykiss) were exposed to 1.5 and 15% v/v secondary treated sewage effluent for 32 weeks in flow-through mesocosms.
The exposure encompassed the full period of reproductive development for rainbow trout.
Trout did not show any evidence of a dose-dependent change in growth.
Fish exposed to 15% effluent were the only group to show mortality (5%) over the duration of the experiment.
Trout at the highest effluent concentration had significantly higher liver size than reference water fish.
Both male and female trout in the 15% exposure group also exhibited significantly higher gonad weight than the reference group.
In female trout, this gonad size increase could be explained by higher egg numbers.
Female and male trout both displayed a significant increase in plasma 17,-estradiol levels after exposure to 15% effluent, while neither sex had dose-dependent differences in plasma testosterone.
Male trout displayed elevated vitellogenin levels and reduced plasma 11-ketotestosterone concentration after exposure to 15% effluent.
Chemical examination of steroidal compounds, including both estrogens and androgens, in the wastewater revealed that only estrone was detectable at a mean concentration of 4.5 ng/L.
It is assumed that the effects observed in trout exposed to 15% effluent were consistent with stimulation of reproductive development due to very low levels of estrogens.
Overall, long-term exposure to treated sewage effluent containing low levels of estrogen did not have significant negative implications for reproductive development in rainbow trout.
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Timing of exposure to a pulp and paper effluent influences the manifestation of reproductive effects in rainbow trout

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2002Michael R. Van den Heuvel
Abstract
Rainbow trout were exposed to a secondary treated, thermomechanical/bleached kraft pulp and paper effluent in 12,000-L, flow-through exposure tanks at an environmental research facility located at a pulp and paper mill in Kawerau, New Zealand.
Trout (age, 2+ years) were obtained from a local hatchery and exposed either to upstream river water or a nominal concentration of 12% (v/v) effluent diluted in upstream river water.
Three treatment groups were used: Effluent exposure that started approximately three months before gonadal growth (eight-month total exposure), effluent exposure that started approximately halfway through gonadal development (two-month total exposure), and trout exposed to reference water alone for the total duration of the experiment.
Trout were sacrificed just before spawning; exposure, growth, and reproductive endpoints were assessed during and at the termination of the experiment.
Reduction in growth was observed in both sexes in the eight-month treatment group relative to the river water reference treatment group.
No differences were observed in condition factor or liver size in either treatment.
Females in the eightmonth exposure group also had significantly lower ovary weight.
The two-month exposure group showed no differences from the reference group in growth or somatic indices.
Estradiol and testosterone were reduced in blood samples taken from the eight-month exposure group by four months into the experiment as compared to the reference treatment.
Steroid and vitellogenin levels in individual female trout from this treatment were significantly correlated with gonadosomatic indices (GSI) measured at the termination of the experiment.
The GSI was not correlated strongly or consistently with pregnenolone, nor were any treatment-related pregnenolone differences observed, indicating that the steroid hormone reductions likely were not related to cholesterol side-chain cleavage.
Male trout showed significant induction of vitellogenin and lower 11-ketotestosterone during the experiment (only the eight-month group was examined), but this did not result in any significant differences in testes development.
Thus, this study has shown an impact of pulp mill effluent exposure on the reproductive physiology of female trout that appeared to be hormonally mediated.
Furthermore, the effect could only be manifest when the exposure was initiated before the start of gonad development.
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ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2001Melissa L. Schwartz
Abstract
Rainbow trout (Oncorhynchus mykiss; 2,17 g) were exposed to approximately 0.1 ,M silver as AgNO3 for 3 to 4 h in synthetic, ion-poor water (20 ,M Ca, 100 ,M Na, 150 ,M Cl, pH 7) to which was added Mg, Ca, or thiosulfate (S2O3).
Gills were extracted and assayed for Ag using graphite furnace atomic absorption spectrophotometry.
Up to 210 mM Mg (four fold the concentration of Mg in seawater) did not reduce accumulation of Ag by trout gills.
The conditional equilibrium stability constant (K) for Mg at silver-binding sites on the gills was calculated to be log KMg-gillAg = 3.0, or approximately half-as-strong binding as for Ca at these sites.
The inclusion of the Mg-gill stability constant into the original Ag-gill binding model increases the flexibility of the model, although the competitive effects of Mg are only important in sodium-poor systems.
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EUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 12 2008Jaime Ortiz
Abstract
The flow ice system including ozone (OFI condition) was tested for slaughtering and storage (up to 16,days) of farmed rainbow trout (Oncorhynchus mykiss).
Lipid damage analyses were carried out and compared to sensory acceptance and instrumental colour changes.
Comparison to individuals processed with the flow ice system in the absence of ozone (FI condition) was undertaken.
Rainbow trout slaughtered and chilled under FI and OFI conditions showed a low lipid damage development, according to lipid oxidation and hydrolysis events and lipid composition (polyunsaturated fatty acids, phospholipids and endogenous antioxidants) changes.
Additionally, both icing conditions led to largely good quality and shelf life times and to the absence of changes in colour properties.
It is concluded that flow ice as such, or including the presence of ozone, can be considered as ideal strategy to be employed as slaughtering and storage system during the commercialisation of the actual farmed species.
The ozone presence has shown some profitable effects as leading to an extended shelf life time by quality retention of several sensory parameters; in contrast, some negligible negative effects could be observed on the secondary and tertiary lipid oxidation development.
However, the oxidation values reached by individuals kept under OFI conditions cannot be considered as particularly high.
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A molecular analysis of hybridization between native westslope cutthroat trout and introduced rainbow trout in southeastern British Columbia, Canada

JOURNAL OF FISH BIOLOGY, Issue 2001E. Rubidge
Restriction site variation in the Ikaros gene intron was used to assess the incidence of westslope cutthroat trout (Oncorhynchus clarki lewisi), rainbow trout (O. mykiss) and interspecific hybrids at 11 localities among eight streams tributary to the upper Kootenay River system in south-eastern British Columbia, Canada.
Out of 356 fish assayed by this technique, hybrids (n=16) were found at seven of the 11 sites across five different streams.
Rainbow trout (n=6) were found at two of the 11 sites.
Analysis of hybrids with a second genetic marker (heat shock 71 intron) indicated that most represented either backcrosses to both westslope cutthroat and rainbow trout, or post F1 hybrids.
Mitochondrial DNA analysis indicated that hybrid matings occur between male rainbow trout and female westslope cutthroat trout and vice versa.
Comparison of present hybridization in five tributaries relative to an allozyme-based analysis in the mid-1980s, that documented hybrids in only a single tributary of seven that were common to the two studies, suggests that hybridization and introgression has increased in upper Kootenay River tributaries.
The present analysis is a conservative estimate of genetic interaction between the species because introgression was not tested in the majority of samples.
Identification of genetically pure westslope cutthroat trout populations, and why they might be resistant to introgression from rainbow trout, are crucial conservation priorities for this unique subspecies of cutthroat trout.
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JOURNAL OF FISH DISEASES, Issue 10 2009R Kocan
Abstract
Rainbow trout, Oncorhynchus mykiss, were infected with Ichthyophonus sp. and held at 10 °C, 15 °C and 20 °C for 28 days to monitor mortality and disease progression.
Infected fish demonstrated more rapid onset of disease, higher parasite load, more severe host tissue reaction and reduced mean-day-to-death at higher temperature.
In a second experiment, Ichthyophonus -infected fish were reared at 15 °C for 16 weeks then subjected to forced swimming at 10 °C, 15 °C and 20 °C.
Stamina improved significantly with increased temperature in uninfected fish; however, this was not observed for infected fish.
The difference in performance between infected and uninfected fish became significant at 15 °C (P = 0.02) and highly significant at 20 °C (P = 0.005).
These results have implications for changes in the ecology of fish diseases in the face of global warming and demonstrate the effects of higher temperature on the progression and severity of ichthyophoniasis as well as on swimming stamina, a critical fitness trait of salmonids.
This study helps explain field observations showing the recent emergence of clinical ichthyophoniasis in Yukon River Chinook salmon later in their spawning migration when water temperatures were high, as well as the apparent failure of a substantial percentage of infected fish to successfully reach their natal spawning areas.
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JOURNAL OF FISH DISEASES, Issue 9 2009D L Merrifield
Abstract
Rainbow trout were fed either a diet containing fishmeal (FM) as the crude protein source or a diet containing 50% replacement with soybean meal (SBM) for 16 weeks.
An enteritis-like effect was observed in the SBM group; villi, enterocytes and microvilli were noticeably damaged compared with the FM group.
The posterior intestine microvilli of SBM-fed fish were significantly shorter and the anterior intestine microvilli significantly less dense than the FM-fed fish.
Electron microscopy confirmed the presence of autochthonous bacterial populations associated with microvilli of both fish groups.
Reduced density of microvilli consequently led to increased exposure of enterocyte tight junctions, which combined with necrotic enterocytes is likely to diminish the protective barrier of the intestinal epithelium.
No significant differences in total viable counts of culturable microbial populations were found between the groups in any of the intestinal regions.
A total of 1500 isolates were tentatively placed into groups or genera, according to standard methods.
Subsequent partial 16S rRNA sequencing revealed species that have not been identified from the rainbow trout intestine previously.
Compared with the FM group levels of Psychrobacter spp. and yeast were considerably higher in the SBM group; a reduction of Aeromonas spp. was also observed.
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The effects of water velocity on the Ceratomyxa shasta infectious cycle

JOURNAL OF FISH DISEASES, Issue 2 2009S J Bjork
Abstract
Ceratomyxa shasta is a myxozoan parasite identified as a contributor to salmon mortality in the Klamath River, USA.
The parasite has a complex life cycle involving a freshwater polychaete, Manayunkia speciosa and a salmonid.
As part of ongoing research on how environmental parameters influence parasite establishment and replication, we designed a laboratory experiment to examine the effect of water flow (velocity) on completion of the C. shasta infectious cycle.
The experiment tested the effect of two water velocities, 0.05 and 0.01 m s,1, on survival and infection of M. speciosa as well as transmission to susceptible rainbow trout and comparatively resistant Klamath River Chinook salmon.
The faster water velocity facilitated the greatest polychaete densities, but the lowest polychaete infection prevalence.
Rainbow trout became infected in all treatments, but at the slower velocity had a shorter mean day to death, indicating a higher infectious dose.
Infection was not detected in Chinook salmon even at a dose estimated to be as high as 80 000 actinospores per fish.
The higher water velocity resulted in lower C. shasta infection prevalence in M. speciosa and decreased infection severity in fish.
Another outcome of our experiment is the description of a system for maintaining and infecting M. speciosa in the laboratory.
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JOURNAL OF FISH DISEASES, Issue 8 2008S Arijo
Abstract
Bacterial subcellular components and probiotics were successful for the stimulation of immunity and the prevention of Vibrio harveyi infections in rainbow trout, Oncorhynchus mykiss (Walbaum).
Rainbow trout were immunized with whole inactivated cells of V. harveyi to obtain polyclonal antibodies against specific antigens.
Western blotting showed a unique reactive band (,93 kDa) between serum and bacterial proteins from outer membrane proteins (OMP) and extracellular products (ECP).
Probiotics were selected according to their capability to inhibit V. harveyi.
Two of these bacteria, i.e. A3-47 and A3-51, showed cross-reactivity with V. harveyi antiserum.
Their OMPs and ECPs were reactive with V. harveyi antiserum in bands of ,93 kDa for A3-51 and higher for A3-47.
In vivo tests determined that fish fed with A3-51 produced cross-reactive antibodies against V. harveyi and also, the survival of these fish infected with V. harveyi was high, being similar to the level achieved with vaccinated fish.
Thus, the probiotics, when administered as live preparations, were capable of producing cross-reactive antibody against specific bacterial pathogens.
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JOURNAL OF FOOD BIOCHEMISTRY, Issue 3 2004CARMEL C. WILLSRainbow trout were killed by two methods, asphyxiation and clubbing.
The concentration of ATP in specimens of skeletal muscle taken immediately after death was significantly (P<0.01) higher in clubbed (4.41 ± 0.86 ,mol/g) than in asphyxiated (2.00 ± 0.69 ,mol/g) fish.
The shear force (Warner-Bratzler) required to cut the muscle was higher (P<0.05) in clubbed (8.33 ± 0.61 N) than in asphyxiated (6.85 ± 0.98 N) fish.
Changes in the concentration of adenine nucleotides and in shear force were measured at intervals during storage at 3C and - 30C.
The K value was calculated and was found to be correlated inversely with changes in shear force, Torrymeter readings and sensory assessment.
There were no significant differences in the concentrations of ATP and metabolites between muscle sites.
There were no differences in shear force measurements between the locations sampled nor between muscle taken from the right and left sides of the fish.
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The effect of hepatic passage on postprandial plasma lipid profile of rainbow trout (Oncorhynchus mykiss) after a single meal

AQUACULTURE NUTRITION, Issue 5 2010E.J. ELIASON
Abstract
For the first time, pre- and post-hepatic plasma lipid profiles were monitored following a single meal in a free-swimming, non-anaesthetized fish.
Rainbow trout (Oncorhynchus mykiss; 700,1500 g; 10 °C) were equipped with cannulae in the dorsal aorta (DA) and hepatic portal vein (HPV).
Simultaneous blood samples, taken from both cannulae at 0, 3, 6, 12, 24 and 48 h postprandial, revealed the time course of the plasma lipid profiles following a single meal (1% of body mass).
Primarily monounsaturated fatty acids with the exception of 18:1n , 9, increased significantly from baseline by 12 h postprandial without greatly affecting total plasma lipid concentrations.
Total plasma lipids then showed a small peak at 24 h postprandial, coinciding with a peak in triacylglycerols.
We conclude that assimilation of lipids from the digest into the plasma is slower than reported for proteins and carbohydrates in the same species.
Furthermore, as there were no significant differences between the HPV and DA, no measurable effect of hepatic passage on plasma lipid levels was resolved.
Therefore, we also conclude that, in contrast to that in higher vertebrates, hepatic passage does not seem to have a major role in rainbow trout for modulating the postprandial plasma profile of lipids.
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AQUACULTURE NUTRITION, Issue 6 2009A. PETTERSSON
Abstract
Increased use of plant oils with different origins and quality in fish feed needs to be approached from a food safety and fish welfare point of view.
Plant oils contain a number of bioactive minor lipid compounds that may affect the fish's metabolism and taste perception.
This study focuses on the effect of replacing fish oil (FO) with different levels of cold-pressed rapeseed oil (RO) on the lipid composition in muscle and liver as well as on the preference by the fish.
Rainbow trout (Oncorhynchus mykiss) were fed diets with a FO : RO ratio of 100 : 0, 75 : 25, 50 : 50 and 25 : 75 until twofold weight increase.
In self-selecting feed trials of single rainbow trout, fish preferred the diet composed of only FO compared with the diets with RO but did not discriminate between different levels of RO.
Plant sterols and their metabolites were found in liver of the fish fed RO diets, suggesting an effect on the sterol metabolism different from fish fed a 100% FO diet.
The largest effects were seen in the fatty acid composition of the edible tissue of the fish with a decrease in 22:6n-3 and 20:5n-3 and an increase in 18:2n-6 and 18:1n-9.
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AQUACULTURE NUTRITION, Issue 4 2001M.J. Apines
A 2 × 4 factorial experiment was conducted to determine the bioavailability of zinc (Zn) from amino acids chelated (Zn,Am) and glass embedded Zn (Zn,Gl) as sources for rainbow trout, Oncorhynchus mykiss, fed practical type diets.
Two levels of Zn (20 and 40 mg kg,1) were supplemented to the diets using either zinc sulphate (Zn,Sf), zinc methionine (Zn,Mt), Zn,Am or Zn,Gl.
Rainbow trout with an average weight of 2 g were fed the experimental diets for 15 weeks.
Growth and feed gain ratio (FGR) were not significantly influenced by the dietary Zn content and forms.
Alkaline phosphatase (ALP) activity for both levels of Zn,Am was significantly higher than that of Zn,Sf and Zn,Gl at 20 mg supplementation.
In another experiment, fish of about 95 g were fed the same experimental diets to determine the absorption of Zn and it was found to be significantly higher from Zn,Am compared with the rest.
Retention from Zn,Am at 20 mg was significantly higher than the rest, excluding Zn,Sf.
The results suggest that the availability of Zn from Zn,Am might be superior among the sources compared.
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Brain distribution of myosin Va in rainbow trout Oncorhynchus mykiss

ACTA ZOOLOGICA, Issue 1 2008Kátia Gisele Oliveira Rancura
Abstract
This study presents data on myosin Va localization in the central nervous system of rainbow trout.
We demonstrate, via immunoblots and immunocytochemistry, the expression of myosin Va in several neuronal populations of forebrain, midbrain, hindbrain and spinal cord.
The neuronal populations that express myosin Va in trout constitute a very diverse group that do not seem to have many specific similarities such as neurotransmitters used, cellular size or length of their processes.
The intensity of the immunoreactivity and the number of immunoreactive cells differ from region to region.
Although there is a broad distribution of myosin Va, it is not present in all neuronal populations.
This result is in agreement with a previous report, which indicated that myosin Va is approximately as abundant as conventional myosin II and kinesin, and it is broadly involved in neuronal motility events such as axoplasmatic transport.
Furthermore, this distribution pattern is in accordance with what was shown in rats and mice; it indicates phylogenetic maintenance of the myosin Va main functions.
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Relationship between stream temperature, thermal refugia and rainbow trout Oncorhynchus mykiss abundance in arid-land streams in the northwestern United States

ECOLOGY OF FRESHWATER FISH, Issue 1 2001J. L. Ebersole
Abstract , Warm stream temperatures may effectively limit the distribution and abundance of Pacific salmon Oncorhynchus spp. in streams.
The role of cold thermal refugia created by upwelling groundwater in mediating this effect has been hypothesized but not quantitatively described.
Between June 21 and September 15, 1994, rainbow trout O. mykiss abundance within 12 northeast Oregon (USA) stream reaches was inversely correlated with mean ambient maximum stream temperatures (r=,0.7, P<0.05).
Some rainbow trout used thermal refugia (1,10 m2 surface area) that were on average 3,8°C colder than ambient stream temperatures.
Within the warmest reaches, high ambient stream temperatures (>22°C) persisted from mid-June through August, and on average 10,40% of rainbow trout were observed within thermal refugia during periods of midday maximum stream temperatures.
Frequency of cold-water patches within reaches was not significantly associated with rainbow trout density after accounting for the influence of ambient stream temperature (P=0.06; extra sum of squares F -test).
Given prolonged high ambient stream temperatures in some reaches, the thermal refugia available in the streams we examined may be too small and too infrequent to sustain high densities of rainbow trout.
However, these refugia could allow some rainbow trout to persist, although at low densities, in warm stream reaches.
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Evidence of concealment behavior by adult rainbow trout and brook trout in winter

ECOLOGY OF FRESHWATER FISH, Issue 3 2000K. A. Meyer
Abstract , There has been little investigation of the winter ecology of adult trout during winter, especially in regard to concealment behavior.
We compared day vs night underwater counts of adult rainbow trout and brook trout from four streams.
At water temperatures between 1°C and 9°C, daytime counts accounted for 44% and 16% of nighttime snorkeling counts for rainbow trout and brook trout adults, respectively.
As winter progressed, nighttime counts declined more so for brook trout than rainbow trout, but the decline was not significant for either species.
Nocturnalism of both species was higher in streams with colder water temperatures.
We observed few fish within concealment structure; however, by electrofishing concealment habitat during the day, we captured 10 times more adult trout than we counted immediately beforehand by snorkeling.
Adult trout were concealed in cobble-boulder substrate and woody debris during the day.,
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Comparative study on sensitivity of higher plants and fish to heavy fuel oil

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2009Lina Gunnarsson
Abstract
Patancheru, near Hyderabad, India, is a major production site for the global bulk drug market.
Approximately 90 manufacturers send their wastewater to a common treatment plant in Patancheru.
Extraordinary high levels of a wide range of pharmaceuticals have recently been demonstrated in the treated effluent.
As little as 0.2% of this effluent can strongly reduce the growth rate of tadpoles, but the underlying mechanisms of toxicity are not known.
To begin addressing how the effluent affects aquatic vertebrates, rainbow trout (Oncorhynchus mykiss) were exposed to 0.2% effluent for 5 d. Several physiological endpoints, together with effects on global hepatic gene expression patterns, were analyzed.
The exposed fish showed both an induction of hepatic cytochrome P450 1A (CYP1A) gene expression, as well as enzyme activity.
Clinical blood chemistry analyses revealed an increase in plasma phosphate levels, which in humans indicates impaired kidney function.
Several oxidative stress-related genes were induced in the livers; however, no significant changes in antioxidant enzyme activities or in the hepatic glutathione levels were found.
Furthermore, estrogen-regulated genes were slightly up-regulated following exposure, and moderate levels of estriol were detected in the effluent.
The present study identifies changes in gene expression triggered by exposure to a high dilution of the effluent, supporting the hypothesis that these fish are responding to chemical exposure.
The pattern of regulated genes may contribute to the identification of mechanisms of sublethal toxicity, as well as illuminate possible causative agents.
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Toxicokinetics of perfluorocarboxylate isomers in rainbow trout

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2009Amila O. De Silva
Abstract
Perfluorooctanoate (PFOA) and other perfluorocarboxylates (PFCAs) are widely dispersed in the environment.
Current and/or historical production of PFOA and fluorochemical precursors was conducted by telomerization and electrochemical fluorination (ECF).
Telomer products typically contain linear chains of perfluorocarbons, and ECF products are a mixture of linear and branched isomers.
The objective of the present study was to examine the role of toxicokinetics on PFCA isomer profiles in fish since monitoring studies have revealed a predominance of n -isomers of PFCAs in biota.
Using dietary exposure, rainbow trout were administered technical ECF PFOA isomers (6.9 ,g/kg/d), linear perfluorononanoate (1.4 ,g/kg/d n -PFNA), and isopropyl PFNA (1.1 ,g/kg/d iso -PFNA) for 36 d and then switched to a 40-d clean diet.
Throughout exposure and depuration phases, blood and tissue sampling ensued.
The accumulation ratio (AR) revealed similar accumulation propensity of n -PFOA and two minor branched PFOA isomers; however, the majority of branched isomers had lower AR values than n -PFOA.
Enrichment of n -PFOA and n -PFNA relative to most branched isomers was consistent in all tissues.
First-order elimination (kd) and half-life (t1/2) values were calculated.
The largest t1/2 corresponded to n -PFNA followed by iso -PFNA.
In ECF PFOA isomers, both n -PFOA and one minor branched isomer had the largest t1/2, suggesting that this minor isomer could be diagnostic of ECF exposure using environmental PFOA isomer patterns.
Results of lower-dose ECF PFOA exposure showed similar results to the high-dose study; it is possible that both scenarios resulted in saturation of processes involved in PFCA transport.
As such, the toxicokinetics of PFCA isomers at environmentally realistic levels may deviate from the results of the present study.
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